1. Field of the Invention
The present invention pertains to techniques for sealing cylindrical bodies to circumscribing conduits. More particularly, the present invention relates to seal assemblies for positioning within, and anchoring to, the interiors of conduits, and finds particular application to apparatus and methods for sealing pipe strings to conduits within wells.
2. Description of Prior Art
Sealing apparatus of various kinds are used in several well working operations, and in the production of a well. For example, in downhole cementing procedures, seal assemblies are used to control the placement of cement and the maintenance of pressure to accomplish cementing operations. Seal assemblies in the form of packers are known for isolating formations for treatment, or for isolating segments of liner or casing for squeeze cementing, for example. Packers are routinely used for sealing production strings to liner or casing to define flow paths from producing formations to the surface. Several packers may be utilized to isolate various formations in a multi-zone producing well. Polished bore receptacles are used in conjunction with annular seal members to provide sliding seals.
Particularly in the case of packers, the seal assembly is usually positioned within a well by means of a pipe string, and then set in sealing and anchoring engagement with the surrounding conduit. The pipe string may be released from anchoring engagement with the packer, and be movable in the well without disturbing the setting of the packer in engagement with the well conduit. The setting operation usually involves the movement of multiple components of the packer to expand one or more resilient seal members, and to wedge anchoring slips against the surrounding well conduit. These operations are controlled from the surface, and may be effected either by manipulation of the pipe string used to carry the packer into the well, or by application of hydraulic pressure through the pipe string to the packer. Retrievable packers are known, and may be released from the well conduit by one or more operations carried out with the pipe string.
Inflatable packers are known for use in unlined wells. In the case of production packers, the seal assemblies used to isolate formations and define flow paths to the surface are set within well casing or liner, which is usually made up to include a sequence of tubular members threaded together or joined by collars.